from math import *
n = int(input())
for i in range(0, n):
	s = input().split()
	a = float(s[0])
	b = float(s[1])
	c = float(s[2])
	p = (a + b + c) / 2
	ans = p * (p - a) * (p - b) * (p - c)
	print("%.2lf" %sqrt(ans))